实现图片的旋转、缩放、切变和位移

实现图片的旋转、缩放、切变、位移功能，效果如下：

	#include "mainwidget.h"
	#include 
	int main(int argc, char *argv[])
	{
		QApplication a(argc, argv);
		MainWidget w;
 		w.show();
   		return a.exec();
 	}

pixitem.h文件

#ifndef PIXITEM_H
#define PIXITEM_H
#include 
#include 
#include 
class PixItem : public QGraphicsItem
{
public:
	PixItem(QPixmap *pixmap);
	QRectF boundingRect() const;
	void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
private:
	QPixmap pix;     		//作为图元显示的图片
};

#endif // PIXITEM_H

pixitem.cpp文件

#include "pixitem.h"
PixItem::PixItem(QPixmap *pixmap)
{
	pix = *pixmap;
}

QRectF PixItem::boundingRect() const
{
	return QRectF(-2-pix.width()/2,-2-pix.height()/2,pix.width()+4, pix.height()+4);
}

void PixItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,QWidget *widget)
{
	painter->drawPixmap(-pix.width()/2,-pix.height()/2,pix);
}

mainwidget.h文件

#ifndef MAINWIDGET_H
#define MAINWIDGET_H

#include 
#include 
#include 
#include 
#include "pixitem.h"

class MainWidget : public QWidget
{
	Q_OBJECT

public:
	MainWidget(QWidget *parent = 0);
 	~MainWidget();
	void createControlFrame();
private:
	int angle;
	qreal scaleValue;
	qreal shearValue;
 	qreal translateValue;
	QGraphicsView *view;
	QFrame *ctrlFrame;
	PixItem *pixItem;
public slots:
	void slotRotate(int);
	void slotScale(int);
	void slotShear(int);
	void slotTranslate(int);
};

#endif // MAINWIDGET_H

mainwidget.cpp文件

#include "mainwidget.h"
#include 
#include 
#include 
#include 
#include 

MainWidget::MainWidget(QWidget *parent)
: QWidget(parent)
{
angle = 0;
scaleValue = 5;
shearValue = 5;
translateValue = 50;

QGraphicsScene *scene = new QGraphicsScene;
scene->setSceneRect(-200,-200,400,400);
QPixmap *pixmap = new  QPixmap("Cherry.png");
pixItem = new PixItem(pixmap);

scene->addItem(pixItem);
pixItem->setPos(0,0);

view = new QGraphicsView;
view->setScene(scene);
view->setMinimumSize(400,400);

ctrlFrame = new QFrame;
createControlFrame();

//主窗口布局
QHBoxLayout *mainLayout = new QHBoxLayout;
mainLayout->setMargin(10);
mainLayout->setSpacing(20);
mainLayout->addWidget(view);
mainLayout->addWidget(ctrlFrame);
setLayout(mainLayout);

setWindowTitle(tr("Graphics Item Transformation"));   //设置主窗体的标题
}

MainWidget::~MainWidget()
{

}

void MainWidget::createControlFrame()
{
//旋转控制
QSlider *rotateSlider = new QSlider;
rotateSlider->setOrientation(Qt::Horizontal);
rotateSlider->setRange(0,360);

QHBoxLayout *rotateLayout = new QHBoxLayout;
rotateLayout->addWidget(rotateSlider);

QGroupBox *rotateGroup = new QGroupBox(tr("Rotate"));
rotateGroup->setLayout(rotateLayout);

//缩放控制
QSlider *scaleSlider = new QSlider;
scaleSlider->setOrientation(Qt::Horizontal);
scaleSlider->setRange(0,2*scaleValue);
scaleSlider->setValue(scaleValue);

QHBoxLayout *scaleLayout = new QHBoxLayout;
scaleLayout->addWidget(scaleSlider);

QGroupBox *scaleGroup = new QGroupBox(tr("Scale"));
scaleGroup->setLayout(scaleLayout);
//切变控制
QSlider *shearSlider = new QSlider;
shearSlider->setOrientation(Qt::Horizontal);
shearSlider->setRange(0,2*shearValue);
shearSlider->setValue(shearValue);

QHBoxLayout *shearLayout = new QHBoxLayout;
shearLayout->addWidget(shearSlider);

QGroupBox *shearGroup = new QGroupBox(tr("Shear"));
shearGroup->setLayout(shearLayout);
//位移控制
QSlider *translateSlider = new QSlider;
translateSlider->setOrientation(Qt::Horizontal);
translateSlider->setRange(0,2*translateValue);
translateSlider->setValue(translateValue);

QHBoxLayout *translateLayout = new QHBoxLayout;
translateLayout->addWidget(translateSlider);

QGroupBox *translateGroup = new QGroupBox(tr("Translate"));
translateGroup->setLayout(translateLayout);

connect(rotateSlider,SIGNAL(valueChanged(int)),this,SLOT(slotRotate(int)));
connect(scaleSlider,SIGNAL(valueChanged(int)),this,SLOT(slotScale(int)));
connect(shearSlider,SIGNAL(valueChanged(int)),this,SLOT(slotShear(int)));
connect(translateSlider,SIGNAL(valueChanged(int)),this,SLOT(slotTranslate(int)));

//控制面板布局
QVBoxLayout *frameLayout = new QVBoxLayout;
frameLayout->setMargin(10);
frameLayout->setSpacing(20);
frameLayout->addWidget(rotateGroup);
frameLayout->addWidget(scaleGroup);
frameLayout->addWidget(shearGroup);
frameLayout->addWidget(translateGroup);
ctrlFrame->setLayout(frameLayout);
}

void MainWidget::slotRotate(int value)
{
view->rotate(value-angle);
angle = value;
}

void MainWidget::slotScale(int value)
{
qreal s;
if(value>scaleValue)
    s=pow(1.1,(value-scaleValue));
else
    s=pow(1/1.1,(scaleValue-value));
view->scale(s,s);
scaleValue=value;
}

void MainWidget::slotShear(int value)
{
view->shear((value-shearValue)/10.0,0);
shearValue=value;
}

void MainWidget::slotTranslate(int value)
{
view->translate(value-translateValue,value-translateValue);
translateValue=value;
}